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Image MIME Reference
Alias-PIX

Alias PIX Image

image/x-alias-pix
VS

Silicon Graphics Image

image/x-rgb
SGI-RGB

A complete technical comparison of Alias PIX Image and Silicon Graphics Image — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.

Equal browser support

Feature Support

Feature Alias-PIX SGI-RGB
Transparency (Alpha) ✕ No Yes
Animation Support ✕ No ✕ No
Progressive Loading ✕ No ✕ No
HDR Support ✕ No ✕ No
EXIF Metadata ✕ No ✕ No
ICC Color Profile ✕ No ✕ No
Alias PIX Image
image/x-alias-pix
Extension
.pix.als.alias.img
Container Alias PIX Header
Compression Run-Length Encoding (RLE)
Algorithm
RLE
Color Depth 24-bit (RGB), 8-bit (Matte/Grayscale variant)
Developed by Alias Research (Later Alias|Wavefront / Autodesk)
Released Early 1990s
Magic Bytes
No explicit magic bytes (Relies on 10-byte integer header)
Full Alias-PIX reference →
Silicon Graphics Image
image/x-rgb
Extension
.rgb.sgi.rgba.bw.int.inta
Container SGI Image Header (512 bytes)
Compression Uncompressed / Run-Length Encoding (RLE)
Algorithm
NoneScanline RLE
Color Depth 8-bit (Per Channel), 16-bit (Per Channel)
Developed by Silicon Graphics, Inc. (Paul Haeberli)
Released 1988
Magic Bytes
01 DA
Full SGI-RGB reference →

Browser Support Comparison

Browser Alias-PIX SGI-RGB
Chrome Chrome
✕ ✕
Firefox Firefox
✕ ✕
Safari Safari
✕ ✕
Edge Edge
✕ ✕
IE IE (Legacy)
✕ ✕
Alias-PIX

Alias-PIX Strengths

  • The highly simplified structure made it incredibly fast to encode and decode on early 1990s SGI hardware
  • Lossless Run-Length Encoding (RLE) saved disk space without degrading the quality of final 3D renders
Limitations
  • Completely obsolete, having been replaced by more robust formats like TIFF, TGA, and EXR in modern 3D pipelines
  • The lack of a distinct magic byte signature makes reliable automated file detection almost impossible
  • Does not support integrated alpha channels, instead requiring cumbersome, separate 'Matte' files to denote transparency
SGI-RGB

SGI-RGB Strengths

  • Supports 16-bit precision per channel and an embedded alpha channel, making it ideal for the demanding compositing workflows of 1990s cinema VFX
  • The scanline-based RLE compression was exceptionally fast to decode on classic MIPS-based SGI workstations
  • Features a straightforward 512-byte header, making it relatively easy to parse and write custom decoders in C or Python
Limitations
  • Completely obsolete and unsupported in modern web environments
  • Replaced entirely by TIFF, OpenEXR, and PNG in modern visual effects and 3D rendering pipelines
  • Lacks support for modern color management via ICC profiles or advanced EXIF metadata

When to choose which format

Alias-PIX
Use Alias-PIX when…
  • Legacy Alias PowerAnimator Textures
  • 1990s SGI Workstation Render Outputs
  • Historical 3D Graphics Archival
SGI-RGB
Use SGI-RGB when…
  • Legacy 3D Animation and VFX Textures
  • Silicon Graphics IRIX Workstation Archival
  • 1990s Medical Imaging

More comparisons

Alias-PIX vs ACES → SGI-RGB vs ACES → Alias-PIX vs APNG → SGI-RGB vs APNG → Alias-PIX vs AVCI → SGI-RGB vs AVCI → Alias-PIX vs AVCS → SGI-RGB vs AVCS → Alias-PIX vs AVIF → SGI-RGB vs AVIF → All comparisons →
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